This invention relates to an actuator for the landing gear assembly of the trailer of a tractor-trailer combination. Conventionally, such a trailer includes a pair of laterally spaced landing gear feet which extend downwardly from the front portion of the trailer and contact the ground to support the trailer in an elevated position when the trailer is detached from the tractor. When the trailer is attached to the tractor, the landing gear feet are retracted upwardly to prevent the feet from engaging the ground while the trailer is being towed by the tractor.
In most trailers, the landing gear feet are connected by a laterally extending cross-shaft which extends the feet when rotated in one direction and retracts the feet when rotated in the opposite direction. The cross-shaft usually is connected to a two-speed gear box located outboard of one of the feet and may be selectively turned at either a high speed or a low speed by a manually operated hand crank attached to the input shaft of the gear box.
It has been recognized that considerable time and effort is required to manually operate the hand crank. Accordingly, power-operated actuators have been provided to rotate the cross-shaft in either direction in order to extend or retract the landing gear feet. One such power-operated landing gear actuator is disclosed in Vandenberg U.S. Pat. No. 4,116,315 and employs a reciprocating pneumatic actuator which is operated by the same source of pressurized air that is used to operate the brakes of the tractor-trailer combination. Another pneumatically operated landing gear actuator has been sold by Northwest Manufacturing Corporation of Camanche, Iowa under the trademark GEAR MATE. That actuator includes two-speed gearing which allows the cross-shaft to be rotated selectively at a high or low speed.